Field rodent · Apodemus sylvaticus · Last updated 14 August 2026
Field mice
The wood mouse (Apodemus sylvaticus) lives outdoors: gardens, vegetable patches, forest edges. It enters homes in autumn to overwinter and stores provisions in its burrows.
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Unlike the house mouse, the field mouse digs branched burrows 50 to 100 cm deep in which it stores seeds, nuts and bulbs. It eats seedlings, root vegetables and bulb plants, causing significant damage to vegetable gardens. In autumn, it moves into garages, basements and attics. It can transmit leptospirosis through its urine.
Identify
Signs of infestation
- Round holes 3 to 4 cm in diameter at the base of walls, hedges or woodpiles
- Stashes of seeds, nuts and berries piled in cavities (a distinctive sign of the wood mouse, absent in rats or house mice)
- Damage to bulbs, seeds and root vegetables in the garden, often overnight
- Droppings of 4 to 6 mm, smaller and paler than a rat's
Where it's found
An edge-dwelling animal (hedges, field margins, banks), the wood mouse (Apodemus sylvaticus) moves into buildings in autumn as the weather turns cold. It settles in cavity walls, under lean-tos and in stored materials. An excellent climber, it can reach the attic.
Impact
Associated risks
LCMV (lymphocytic choriomeningitis)
A virus transmitted by contact with wood mouse urine, droppings or nest dust. Mild in healthy adults, but potentially serious for immunocompromised people and pregnant women (foetal risk).
Garden and storage damage
The wood mouse gnaws bulbs, germinating seeds, cables and insulation. Its hidden stashes attract other pests (flour mites, weevils).
Good practice
Prevention
- 01Seal cellar vents and cable runs before October, the main entry period for wood mice moving indoors
- 02Store garden seeds in airtight metal containers, never in bags
- 03Keep woodpiles, compost and stored materials at least 50 cm from the walls
Frequently asked questions
What you're asking
How do I tell a field mouse from a house mouse?
The field mouse is larger (8–10 cm body) with large prominent black eyes, big ears and a two-tone coat — russet brown on top, off-white on the belly. Its developed hind legs let it leap. The house mouse is smaller, uniform grey-brown, and lives indoors year-round.
Is the field mouse dangerous to health?
Yes. Its urine can contain Leptospira interrogans, the bacterium responsible for leptospirosis (fever, jaundice, kidney damage). The risk is small but real, particularly for gardeners without gloves and owners of infested basements. Licensed rodenticides must be used in a food-safe manner.
Can I just leave field mice in my garden?
In small numbers, their impact is limited. But an uncontrolled population systematically destroys bulbs, seedlings and root vegetables. In autumn, they colonise buildings. Preventive treatment from September onwards is recommended for vegetable gardens.
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